there is an code comment inside of AlCombatRules that reads

"Unlike protection bypass, additional armor bypass will cause unarmored targets to take additional damage."

this is not the case. Both an casual look at the code in question and in-game testing reveals that against an target with 0 armor points, there is no difference between having armor pierce / armor shred and not having armor pierce / armor shred.

Hm, yeah. Seems that's been inoperable for a while. I'll have to add a new mechanism for it.